The invention relates to a clutch, in particular for a power train of a motor vehicle. The clutch has an input shaft supporting a flywheel with a substantially ring-shaped friction surface and an output shaft supporting a clutch disc with a friction lining conforming to the friction surface of the flywheel. The flywheel is constrained to rotate together with the input shaft, and the clutch disc is constrained to rotate with the output shaft. The clutch further has an axially movable pressure plate and an actuator device that serves to move the pressure plate and thereby engage and disengage the clutch. In the engaged position, the pressure plate is urging the clutch disc into friction-locked compressive contact against the flywheel. In the disengaged position, the pressure plate is retracted, whereby the friction-lock between the input shaft and the output shaft is interrupted. The aforementioned components are enclosed in a housing with openings for the input shaft and the output shaft to pass through.
FIG. 5 provides a general orientation of the layout and function of a motor vehicle clutch. An input shaft 2 originating from a source of motive power, e.g., the crankshaft of an engine, carries a flywheel 4 that is constrained on the input shaft to share its rotation. The flywheel 4, which generally performs the function of an engine flywheel, extends as a disc from the input shaft to an outer circumference where its contour turns into the axial direction to form a cylindrical wall, ending in a radially inward bent rim that forms an abutment ring 6. Running axially in line with the input shaft 2 is an output shaft 8. A clutch disc 10 is attached to the output shaft through a rotationally fixed connection. The radially outer portion of the clutch disc 10 carries a substantially ring-shaped friction lining 12 designed to engage a corresponding friction surface of the flywheel 4. The flywheel 4 can likewise be equipped with a friction lining.
The clutch disc 10 is axially movable in relation to the output shaft 8, or flexibly deformable in the axial direction. A pressure disc or pressure plate 14 that is axially movable in relation to the output shaft 8 and can be rotationally constrained to the latter serves to press the clutch disc 10 against the flywheel 4. Normally, a diaphragm spring 16, seated at its outer circumference against the abutment ring 6, pushes the pressure plate 14 against the clutch disc 10, so that the latter is in non-slipping frictional engagement with the flywheel 4. The radially inner border of the diaphragm spring is held in a retracting ring 18 that is rotatably supported on an actuator ring 20. The actuator ring 20 is axially movable on the output shaft 8 by means of an actuator mechanism 22. By moving the actuator ring 20 to the right (as shown in FIG. 5) the diaphragm spring 16 is caused to change its shape so that the pressure plate 14 is no longer pushed against the clutch disc 10 and the clutch is taken out of engagement. The entire arrangement is accommodated in a housing 24 that is formed by a so-called clutch bell 26 and the engine housing 28. The clutch bell 26, covering the side of the clutch facing towards the transmission, is attached to the engine housing 28.
Mechanical clutches of this kind, which include one or more flywheels, have to meet exacting requirements. The clutch is expected to engage softly, to transmit large amounts of torque, and to have a long operational life span. If the clutch is used in conjunction with automated shift transmissions, in particular with transmissions that shift under load, where several gear shifts can occur in rapid succession under a high torque load, large amounts of heat may be generated in the clutch, which can be detrimental to its functionality and shorten its useful life.
It is therefore the object of the present invention to further develop a clutch of the kind described above in order to increase the rate at which the clutch can convert mechanical energy into thermal energy without suffering damage.
According to the invention, the foregoing objective is met by a clutch in which the flywheel has fan blades arranged at least in a zone that is radially inside the friction surface, so that the rotation of the flywheel will cause an air stream to flow over the side of the flywheel that faces away from the friction surface.
In a clutch designed in accordance with the invention, the air stream will carry the heat away significantly faster, so that even at a high rate of heat generation, the friction linings will remain at a low temperature and will therefore not be exposed to the risk of being damaged.
In a preferred embodiment of the invention, the flywheel, the clutch disc and the pressure plate have air passages located in a radial zone between the output shaft and the friction lining. This allows the air stream generated by the fan blades of the flywheel to flow axially along the output shaft.
Also preferred according to the invention is a configuration of the clutch where the housing surrounds the flywheel, the clutch disc and the pressure plate at a sufficient distance for the air to circulate in a closed loop. Passing through the aforementioned air passages in the flywheel, the clutch disc and the pressure plate, the air will move in an axial direction along the output shaft from the pressure plate to the flywheel, then turn radially outwards and continue its circulation path between the housing and the flywheel, then turn into the axial direction along the peripheral housing wall from the flywheel to the pressure plate, and finally turn back inwards in the radial direction to complete the loop of air circulation.
In another preferred embodiment of the invention, the housing has an air inlet and an air outlet. In this case, outside air enters the housing through the inlet, then flows on a path inside the housing that leads through the flywheel, and leaves the housing through the air outlet.
In the embodiment of the preceding paragraph, a preferred location for the air inlet is on the side of the housing that is farther away from the flywheel, while the air outlet is located preferably in a peripheral housing wall, so that the air flow path runs in an axial direction from the air inlet along the output shaft, passes through the flywheel, then turns into an outward radial direction between the housing and the flywheel and exits from the housing through the air outlet.
In a clutch according to the invention, it is advantageous if the housing has an interior surface that is provided with cooling fins.
In clutches according to the invention, it is preferred if the flywheel performs the function of an engine flywheel.
In preferred embodiments of the invention, it is of advantage if the flywheel is provided with cooling fins.
As a further advantageous concept within the scope of the invention, a clutch may have two or more flywheels, clutch discs and pressure plates arranged in an alternating line-up along the rotational axis of the clutch.
In an advantageous practical embodiment of the foregoing concept, the clutch has one input shaft and two output shafts. The first output shaft runs coaxially inside the hollow second output shaft. The aforementioned alternating line-up, starting from the side of the input shaft, includes:
a first flywheel rotationally fixed on the input shaft;
a first clutch disc rotationally fixed on the first output shaft;
a first pressure plate operable by means of an actuator mechanism to actuate the first clutch disc;
a second flywheel rotationally fixed on the input shaft;
a second clutch disc rotationally fixed on the second output shaft; and
a second pressure plate operable by means of the actuator mechanism to actuate the second clutch disc.
The novel features that are considered as characteristic of the invention are set forth in particular in the appended claims. The improved apparatus itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain presently preferred specific embodiments with reference to the accompanying drawing.